1. Field of the Invention
The present invention relates to a bonding wire and a method for manufacturing the same. Particularly, the present invention relates to a bonding wire having a core member mainly composed of copper; and a palladium coating layer or a coating layer of palladium and gold, and a method for manufacturing the same.
2. Description of Related Art
Conventionally, there has been known a palladium-coated copper bonding wire (e.g. Japanese Patent No. 4158928) obtained by coating a core member mainly composed of copper with palladium.
A palladium-coated copper bonding wire for commercial use is often heated through a plasma arc under a nitrogen gas atmosphere, followed by performing ultrasonic thermocompression bonding to bond a ball that is formed through melting and solidification to an aluminum pad on a semiconductor device. When forming a ball under a nitrogen gas atmosphere, efforts have been made to maintain a sphericity of a melted ball before solidifying by adding to a copper core member phosphorus as a deoxidizing agent such that a surface tension of a ball surface can be maintained as a result of preventing oxidation of copper if exposed when forming the ball.
Due to the continuous efforts that have been made, there are now various types of packaging using a palladium-coated copper wire in recent days. In fact, palladium-coated copper wires are used more often than before even to perform packaging requiring a high reliability.